US7856195B2 - Image forming apparatus whose image bearing member is rotated by a pulley - Google Patents

Image forming apparatus whose image bearing member is rotated by a pulley Download PDF

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Publication number
US7856195B2
US7856195B2 US11/953,376 US95337607A US7856195B2 US 7856195 B2 US7856195 B2 US 7856195B2 US 95337607 A US95337607 A US 95337607A US 7856195 B2 US7856195 B2 US 7856195B2
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Prior art keywords
pulley
belt
pressing
pulleys
rotation axis
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Expired - Fee Related, expires
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US11/953,376
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English (en)
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US20080145101A1 (en
Inventor
Masaki Seto
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Canon Inc
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Canon Inc
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Assigned to CANON KABUSHIKI KAISHA reassignment CANON KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SETO, MASAKI
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/75—Details relating to xerographic drum, band or plate, e.g. replacing, testing
    • G03G15/757—Drive mechanisms for photosensitive medium, e.g. gears
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/01—Apparatus for electrographic processes using a charge pattern for producing multicoloured copies
    • G03G15/0142—Structure of complete machines
    • G03G15/0178—Structure of complete machines using more than one reusable electrographic recording member, e.g. one for every monocolour image
    • G03G15/0194—Structure of complete machines using more than one reusable electrographic recording member, e.g. one for every monocolour image primary transfer to the final recording medium
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2215/00—Apparatus for electrophotographic processes
    • G03G2215/01—Apparatus for electrophotographic processes for producing multicoloured copies
    • G03G2215/0103—Plural electrographic recording members
    • G03G2215/0119—Linear arrangement adjacent plural transfer points
    • G03G2215/0122—Linear arrangement adjacent plural transfer points primary transfer to an intermediate transfer belt
    • G03G2215/0125—Linear arrangement adjacent plural transfer points primary transfer to an intermediate transfer belt the linear arrangement being horizontal or slanted
    • G03G2215/0132—Linear arrangement adjacent plural transfer points primary transfer to an intermediate transfer belt the linear arrangement being horizontal or slanted vertical medium transport path at the secondary transfer

Definitions

  • the present invention relates to a drive transmission apparatus (belt drive transmission apparatus) suitable for use in precision equipment represented by an image forming apparatus such as a copying machine, a laser beam printer, or a facsimile apparatus.
  • a drive transmission apparatus (belt drive transmission apparatus) suitable for use in precision equipment represented by an image forming apparatus such as a copying machine, a laser beam printer, or a facsimile apparatus.
  • a color image forming apparatus As a representative example of the precision equipment, a color image forming apparatus will be described.
  • a color image forming apparatus in which a plurality of image forming stations for forming toner images different in color are arranged along a movement direction of a recording material conveying belt or an intermediary transfer belt.
  • these belts are collectively referred to as a “transfer belt”.
  • a drive transmission apparatus driving force transmitting apparatus
  • a gear speed reducing mechanism as a speed reducing mechanism for rotating a photosensitive drum shaft from a motor shaft are principally used.
  • a motor and a gear speed reducing mechanism for transmitting a driving force to a transfer belt driving roller are used as a drive transmission apparatus for a transfer belt.
  • the transfer belt is moved by rotation of the transfer belt driving roller.
  • Image carrying members (the photosensitive drum and the transfer belt) as rotatable member, which are rotated or moved by the above-described motors and mechanisms, may generally desirably be stably driven at a constant speed in order to ensure image accuracy with high precision. Therefore, an image is transferred onto a recording material while being positioned with high precision, so that a high-quality output image free from color shift, image non-uniformity, and positional deviation is obtained as a resultant product.
  • gears for transmitting a drive force are susceptible to engaging pitch non-uniformity between the gears, which affects the rotation of the photosensitive drum or the transfer belt.
  • a drive transmission mechanism using a belt may preferably be used for reducing the effect of the pitch non-uniformity on the image.
  • JP-A Hei 06-161205 discloses a constitution in which a plurality of belts is connected while the driving force from a motor shaft as a driving source is divided.
  • the belt tension is increased in some cases.
  • shaft tilt can be caused to occur by the belt tension.
  • the shaft tilt can change the driving speed to cause the occurrence of image non-uniformity due to a color shift or a partial reduction in image magnification.
  • JP-A 2004-183860 discloses a constitution in which a center distance or parallelism is accurately defined with respect to two supporting frames.
  • JP-A Sho 62-80648 discloses a constitution in which a plurality of pulleys contacts a pulley for supporting a belt by the medium of the belt.
  • a force toward another pulley is exerted by tension of the belt, but this arrangement of the plurality of pulleys cannot sufficiently reduce the load by the belt tension on the drive shaft which supports the belt.
  • a principal object of the present invention is to provide an image forming apparatus capable of alleviating a load on a shaft by tension of a belt to enhance rotation stability of a pulley in a drive transmission apparatus using the pulley and the belt.
  • an image forming apparatus for forming an image on a recording material, comprising: an image bearing member;
  • FIG. 1 is a schematic structural view of an image forming apparatus in Embodiment 1.
  • FIGS. 2 and 3 are schematic views each for illustrating a drum driving system and a transfer belt driving system.
  • FIG. 4 is a schematic perspective view of a speed reducing mechanism portion of the drum driving system.
  • FIG. 5 is a schematic front view of the speed reducing mechanism portion of the drum driving system.
  • FIGS. 6 to 8 are schematic views each for illustrating a relationship between a belt tension and a back-up force.
  • FIG. 9 is a partially enlarged sectional view of a driving pulley and a back-up pulley which contact each other through a belt.
  • FIG. 10 is a schematic front view of a speed reducing mechanism portion of a transfer belt driving system.
  • FIG. 11 is a schematic perspective view of a speed reducing mechanism portion of a drum driving system in Embodiment 2.
  • FIG. 1 is a schematic structural view showing an embodiment of an image forming apparatus using a belt drive transmission apparatus according to the present invention.
  • the image forming apparatus of this embodiment is a four-color based full-color copying machine employing electrophotography, and the apparatus employs a laser beam scanning exposure method, and an intermediary transfer method.
  • the image forming apparatus includes a reader portion 1 R and a printer portion 1 P, which includes four image forming stations provided in a tandem arrangement.
  • the reader portion 1 R is an image reader for photoelectrically reading image information on an original.
  • An original O to be copied is placed upside down on an original supporting plate glass 81 in accordance with a predetermined placing reference and is covered with an original cover plate 82 .
  • an image reading mechanism portion 83 is actuated to photoelectrically read a downward image surface of the original O on the glass 81 .
  • the image reading mechanism portion 83 is an image reader of an optical system movement type including an original illumination light source 84 , reflection mirrors 85 - 87 , an imaging lens system 88 , an image reading element 89 , such as a CCD array or the like, etc. Electrical information of the original image photoelectrically read by the image reading element 89 is inputted into a control unit 70 through an image processing portion 71 to provide an image-modulated digital image signal.
  • the printer portion 1 P roughly includes an image forming portion 10 , a sheet feeding unit 20 , an intermediary transfer unit 30 , a fixing unit 40 , the control unit 70 , etc.
  • the image forming portion 10 includes four image forming stations a, b, c and d having the same constitution.
  • a drum-type electrophotographic photosensitive member hereinafter referred to as a “drum”
  • 11 a , 11 b , 11 c or 11 d is supported by a drum shaft and rotationally driven in a counterclockwise direction indicated by an arrow by a belt drive transmission apparatus as a drum driving system described later.
  • peripheral members including primary charges 12 a to 12 d , optical systems 13 a to 13 d , fold-back minors 16 a to 16 c , developing devices 14 a to 14 d , and drum cleaning apparatuses 15 to 15 d are disposed opposite to outer peripheral surfaces of the drums 11 a to 11 d with respect to a drum rotational direction.
  • the surfaces of the drums 11 a - 11 d are electrically charged uniformly by the primary charges 12 a - 12 d to a predetermined polarity and a predetermined potential.
  • the drum surfaces after the charging are exposed to light by the optical systems 13 a - 13 d to form thereon electrostatic latent images.
  • Each of the optical systems 13 a - 13 d is a laser scanning exposure apparatus in this embodiment and includes a laser light source, a polygonal minor, and the like.
  • Each of the optical systems 13 a - 13 d outputs laser light (beam) modulated corresponding to a digital image signal inputted from the control unit 70 , so that each of the surfaces of the drums 11 a - 11 d is subjected to scanning exposure with the laser light through one of the associated fold-back minors 16 a - 16 d.
  • the electrostatic latent images formed on the drums 11 a - 11 d are developed into toner images by the developing devices 14 a - 14 d accommodating toners (developers) of black (Bk), magenta (M), cyan (C), and yellow (Y), respectively. These toner images are transferred onto an endless type intermediary transfer belt 31 as a second image carrying member rotationally driven in a direction indicated by an arrow B at primary transfer areas Ta, Tb, Tc and Tb in the intermediary transfer unit 30 . Toner remaining on the drums 11 a - 11 d without being transferred onto the transfer belt 31 are removed from the drum surfaces by the drum cleaning apparatuses 15 a - 15 d . As a result, the surfaces of the drums 11 a - 11 d are cleaned and repeatedly subjected to image formation.
  • the above described image forming process is carried out at a predetermined control timing at each of the stations a-d, so that formation of the toner images of yellow, cyan, magenta and black is successively performed.
  • the sheet-feeding unit 20 includes upper and lower (first and second) sheet-feeding cassettes 21 a and 21 b and a manual feeding tray 27 in which sheets of a recording material (a sheet like recording material or a recording medium) P are stacked and accommodated.
  • the sheet-feeding unit 20 further includes pick up rollers 21 a , 21 b and 26 for feeding the recording material P one by one from the sheet-feeding cassette 21 c and 21 b and the mutual feeding tray 26 .
  • the unit 20 further includes a sheet-feeding roller pair 23 and a sheet-feeding guide 24 for conveying the recording material P fed from the respective pick up rollers to a registration roller pair 25 a and 25 b .
  • the registration roller pair 25 a and 25 b are opposing rollers for sending the recording material P to a secondary transfer area Te with predetermined control timing.
  • the intermediary transfer unit 30 is provided with an endless transfer belt 31 as the intermediary transfer member.
  • the transfer belt 31 is extended around three rollers consisting of a driving roller 33 for transmitting drive (driving force) to the belt, a tension roller 32 for imparting tension to the belt, and a secondary transfer opposing roller 34 . Between the driving roller 33 and the tension roller 32 , a primary transfer plane A is formed.
  • chargers 35 a - 35 d for primary transfer are disposed on a back surface (inner peripheral surface) of the belt 31 so that they are located opposite to the drums 11 a - 11 d , respectively, through the belt 31 .
  • the transfer belt 31 is rotationally driven by the driving roller 33 actuated by a belt drive transmission apparatus as a transfer belt driving system described later.
  • the driving roller 33 is prepared by coating a surface of a metal roller with a layer of rubber material (urethane or chloroprene rubber) in a thickness of several mm to prevent slip with respect to the transfer belt 31 .
  • the tension roller 32 and the secondary transfer opposing roller 34 are rotated by the rotation of the transfer belt 31 .
  • a secondary transfer roller 36 is disposed oppositely to form the secondary transfer area Te in a nip between the rollers 34 and 36 .
  • the secondary transfer roller 36 is pressed against the transfer belt 31 at an appropriate pressure.
  • a belt cleaning apparatus 50 for cleaning the surface of the transfer belt 31 is disposed.
  • the belt cleaning apparatus 50 includes a cleaning blade 51 for removing secondary transfer residual toner deposited on an image forming surface of the transfer belt 31 and a waste toner box 52 for containing the removed secondary transfer residual toner as waste toner.
  • the fixing unit 40 includes a fixing roller portion 46 having a fixing roller 41 a containing a heat source and a pressing roller portion 47 , having a pressing roller 41 b containing a heat source, brought into contact with the fixing roller 41 a.
  • the recording material P which has passed through the secondary transfer area Te is guided by a guide 43 and introduced into a fixing nip.
  • the recording material P coming out of the fixing nip is discharged out of the fixing unit 40 by inner sheet discharging rollers 44 and is further discharged on a sheet discharge tray 48 through outer sheet discharging rollers 45 .
  • the control unit 70 includes a control board for controlling operations of the mechanisms in the above-described respective units and a motor drive board (not shown).
  • the recording material P is fed one by one from, e.g., the first sheet-feeding cassette 21 a by a pick up roller 22 a .
  • the fed recording material P is guided in the sheet-feeding guide 24 by the sheet-feeding roller pair 23 to be conveyed to the registration roller pair 25 a and 25 b .
  • rotation of the registration roller pair 25 a and 25 b is stopped, so that a leading end of the recording material P reaches a nip between the rollers 25 a and 25 b .
  • the rotation of the registration roller pair 25 a and 25 b is started.
  • This rotation start timing is set so that the leading end of the recording material P coincides with a leading end of the superposed toner images primary-transferred from the respective stations a-d onto the transfer belt 31 , in the secondary transfer area Te.
  • a yellow toner image formed on the drum 11 d at the most upstream-side station d with respect to the rotational direction of the transfer belt 31 is primary-transferred onto the transfer belt 31 in the primary transfer area Td by the charger 35 d for primary transfer to which a high voltage is applied.
  • the yellow toner image primary-transferred onto the transfer belt 31 is conveyed to a subsequent (adjacent) primary transfer area Tc.
  • the image forming process is performed with a delay of the time required for conveying the toner image between adjacent two stations, so that a current toner image is transferred and superposed on a preceding toner image in registration. This operation is repeated until the final toner image is primary-transferred, so that four-color toner images consisting of the yellow toner image, cyan toner image, magenta toner image, and black toner image are finally primary-transferred onto the transfer belt 31 in a superposition manner.
  • the recording material P is accurately guided into the fixing nip between the fixing roller 431 a and the pressing roller 41 b .
  • the recording material P is heated and pressed by these rollers 41 a and 41 b , so that the toner image is fixed on the surface of the recording material P.
  • the recording material P is discharged on the sheet discharge tray 48 by the inner and outer sheet discharging rollers 44 and 45 .
  • FIGS. 2 and 3 are schematic views showing a driving system 110 for the drums 11 a - 11 d at the image forming portion 10 and a driving system 210 for the transfer belt 31 at the intermediary transfer unit 30 .
  • the drums 11 a - 11 d are arranged in parallel between first and second opposing side plates 2 a and 2 b of a casing (frame or chassis) of the image forming apparatus while being rotatably held at both ends of drum shafts 111 a - 111 d through bearing members 3 .
  • a rotational force of a motor shaft 115 a of a drum driving motor (driving source) is transmitted by the belt drive transmission apparatus as the drum driving system 110 , so that the drums 11 a - 11 d are driven in a predetermined identical direction at a predetermined identical speed.
  • the motor 115 is stationarily fixed and disposed on a third side plate 2 c located opposite to the second side plate 2 b .
  • a driving motor pulley (driving pulley) 117 is concentrically integrally fixed and disposed.
  • an idler pulley shaft 5 as a rotatable member is rotatably held at both ends thereof through bearing members 4 .
  • first to fifth (five) idler pulleys (follower pulleys) 112 and 112 a - 112 d are concentrically integrally provided.
  • drum pulleys 118 a - 118 d are fixedly disposed at the second side plate 2 b side.
  • the center of the rotatable member (rotation axis) substantially coincides with the center of the idler pulleys.
  • a drive transmission belt 116 which is a metal-made flat belt is stretched. Further, tensioner rollers 120 a and 120 b for applying tension to the belt 116 and back-up pulleys (pressing members) 119 a and 119 b for preventing shaft tilting, of the motor shaft 115 a as the driving shaft, caused by the tension of the belt 116 are disposed. These tensioner rollers 120 a and 120 b and the back-up pulleys 119 and 119 b are specifically described later.
  • a center line of the driving shaft substantially coincides with a shaft axis of the driving pulley. Further, the shaft axis of the driving pulley coincides with a rotation axis of the driving pulley.
  • a belt 113 a which is a metal-made flat belt is stretched.
  • tension is applied by a tensioner roller 114 a .
  • a belt 113 b which is a metal-made flat belt is stretched.
  • tension is applied by a tensioner roller 114 b .
  • a belt 113 c which is a metal-made flat belt is stretched.
  • tension is applied by a tensioner roller 114 c .
  • a belt 113 d which is a metal-made flat belt is stretched.
  • tension is applied by a tensioner roller 114 d.
  • the first idler pulley 112 is a large diameter pulley.
  • the first to fifth idler pulleys 112 and 112 a - 112 d and the drum pulleys 118 a - 118 d are identical diameter pulleys.
  • the axes of the motor shaft 115 a , the idler pulley shaft 5 , and the drum shafts 111 a - 111 d are parallel to each other.
  • a rotational force of the motor shaft 115 a of the motor 115 is transmitted to the first idler pulley 112 through the driving pulley 117 and the belt 116 to rotationally drive the idler pulley shaft 5 .
  • the diameter of the first idler pulley 112 is larger than that of the driving pulley 117 , so that a rotational speed of the motor shaft 115 a is reduced and transmitted to the idler pulley shaft 5 .
  • rotation of the second idler pulley 112 a is transmitted to the drum shaft 111 a through the belt 113 a and the drum pulley 118 a thereby the rotationally drive the drum 11 a .
  • rotation of the third idler pulley 112 b is transmitted to the drum shaft 111 b through the belt 113 b and the drum pulley 118 b thereby the rotationally drive the drum 11 b .
  • rotation of the fourth idler pulley 112 c is transmitted to the drum shaft 111 c through the belt 113 c and the drum pulley 118 c thereby the rotationally drive the drum 11 c .
  • rotation of the fifth idler pulley 112 d is transmitted to the drum shaft 111 d through the belt 113 d and the drum pulley 118 d thereby the rotationally drive the drum 11 d.
  • the driving roller 33 for rotationally driving the transfer belt 31 is rotatably held and disposed between the first and second side plates 2 a and 2 b of the apparatus casing at both end portions of the roller shaft 33 a through bearing members 6 .
  • the secondary transfer opposing roller 34 is rotatably held between the first and second side plates 2 a and 2 b of the apparatus casing at both end portions of the roller shaft 34 a through bearing members and is disposed in parallel to the driving roller 34 .
  • the tension roller 32 is rotatably held by bearing members 7 movably supporting both end portions of a roller shaft 32 a and moves and urges the bearing members 7 in a direction in which tension is applied to the transfer belt 31 .
  • the axes of the driving roller 33 , the secondary transfer opposing roller 34 , and the tension roller 32 are parallel to the axes of the drum shafts 111 a - 111 d.
  • a rotational force of a motor shaft 201 a of a transfer belt driving motor (driving source) 201 is transmitted to the roller shaft 33 a of the driving roller 33 by a belt drive transmission apparatus as the transfer belt driving system 210 , so that the transfer belt 31 is driven in a predetermined rotational direction at a predetermined rotational speed.
  • the motor 201 is stationarily fixed and provided to a fifth side plate 2 e located opposite to the second side plate 2 b .
  • a driving pulley 202 is concentrically integrally fixed and provided.
  • a transfer belt pulley 203 is fixedly disposed.
  • a drive transmission belt 204 which is a metal-made flat belt is stretched.
  • tensioner rollers 205 a and 205 b for applying tension to the belt 204 and back-up pulleys (pressing members) 206 a and 206 b for preventing shaft tilting of the motor shaft 201 a caused by the tension of the belt 204 and disposed.
  • These tensioner rollers 205 a and 205 b and the back-up pulleys 206 a and 206 b are specifically described later.
  • the axes of the motor shaft 201 a and the roller shaft 33 a of the driving roller 33 are parallel to each other.
  • the transfer belt pulley 203 is large diameter pulley.
  • a rotational force of the motor shaft 201 a of the motor 201 is transmitted to the transfer belt pulley 203 through the driving pulley 202 and the belt 204 to rotationally drive the roller shaft 33 a of the driving roller 33 .
  • the diameter of the transfer belt pulley 203 is larger than that of the driving pulley 202 , so that the rotational speed of the motor shaft 201 a is reduced and transmitted to the roller shaft 33 a thereby, to rotationally drive the driving roller 33 .
  • the transfer belt 31 is driven in a predetermined rotational direction at a predetermined rotational speed.
  • a rotational speed of the motor shaft 115 a of the drum driving motor (driving source) 115 is transmitted through the driving pulley 117 (first pulley), the first idler pulley 112 (second pulley) which has a larger diameter than that of the driving pulley 117 , and the belt 116 stretched between the pulleys 117 and 112 .
  • the rotational speed of the drums 11 a - 11 d is slower than the rated speed of a general-purpose DC motor or pulse motor as the drum driving motor 115 .
  • a large drive load torque is exerted by a contact load of the cleaning members 15 a - 15 b against the drums and adsorption of the transfer belt with respect to the drums by high voltage application at the transfer portions Ta-Td. For this reason, driving force transmission from the motor 115 to the drums 11 a - 11 d requires ensuring of a torque margin by a speed reducing mechanism.
  • FIG. 4 is a schematic perspective view of the above-described speed reducing mechanism portion in the drum driving system 110 and FIG. 5 is schematic front view of the speed reducing mechanism portion.
  • a reference symbol C represents a line connecting a center (rotation axis) D of the driving pulley 117 as a drive-side pulley and a center (rotation axis) E of the first idler pulley 112 as a follower-side pulley.
  • the tensioner rollers 120 a and 120 b for applying tension to the belt 116 stretched between the driving pulley 117 and the idler pulley 112 are disposed at substantially symmetrical positions with respect to the axis C. These tensioner rollers 120 a and 120 b are pressed against the outer surface of the belt 116 by tension springs 121 a and 121 b , respectively, to the tension to the belt 116 .
  • the belt tension applied by the tensioner rollers 120 a and 120 b can be calculated from an arrangement and pressing forces of the tensioner rollers 120 a and 120 b.
  • the metal-mode flat belt is used as the drive transmission belt 116 .
  • a metal-made flat or V belt free from engaging tooth is used and a high tension is applied to the belt, so that pitch non-uniformity caused by the engaging tooth does not occur with the result that a high drive transmission torque can be ensured.
  • the metal-made flat belt is used as the belt 116 , so that a high tension is required.
  • a pulley radius of the driving pulley 117 as the drive-side pulley is constituted so as to be smaller than that of the idler pulley 112 as the follower-side pulley, so that the motor shaft 115 a of the motor 115 has a relatively small diameter.
  • the motor shaft 115 a having low rigidity can cause shaft tilting by the action of the high tension. Therefore, the problem of the shaft tilting is solved by providing the back-up pulleys (pressing members) 119 a and 119 b for alleviating the shaft tilting of the motor shaft 115 a.
  • the back-up pulleys 119 a and 119 b are disposed at substantially symmetrical positions with respect to the above-described axis C and are pressed against the driving pulley 117 through the belt 116 interposed therebetween.
  • the symmetrical positions mean positions providing substantially equal angles ⁇ 1 and ⁇ 2 when the angle ⁇ 1 is formed between the line C and a line connecting the center (rotation axis) D of the driving pulley 117 and a center (rotation axis) G of the back-up pulley 119 a and the angle ⁇ 2 is formed between the line C and a line connecting the center D of the driving pulley 117 and a center (rotation axis) H of the back-up pulley 119 b .
  • back-up pulleys 119 a and 119 b are disposed at an upstream side and a downstream side, respectively, with respect to the rotational direction of the belt 116 extended around the driving pulley 117 . Further, in this embodiment, the back-up pulleys 119 a and 119 b are disposed so as to not only increase the winding amount of the belt 116 around the driving pulley 117 but also be pressed substantially from the idler pulley 112 side toward the shaft axis of the driving pulley 117 . The pressing portions of the back-up pulleys against the driving pulley are located closer to the idler pulley than the rotation center (rotation axis) of the driving pulley.
  • the back-up pulleys 119 a and 119 b are rotatably supported by rotatably swingable arms 123 a and 123 b , respectively, with shaft portions 122 a and 122 b as centers of the rotation.
  • swingable arms 123 a and 123 b are rotationally urged toward the driving pulley 117 by pressing springs 124 a and 124 b , respectively, to press the back-up pulleys 119 a and 119 b against the driving pulley 117 through the belt 116 .
  • the back-up pulleys 119 a and 119 b apply back-up forces from outside of the belt 116 to the driving pulley 117 so that the resultant of forces is zero in a force relationship with the belt tension.
  • this can be easily designed by obtaining forces acting on the driving pulley 117 to determine the back-up forces of the back-up pulleys 119 a and 119 b in the following manner.
  • belt tensions T are obtained as components of forces of belt winding angles.
  • the belt tensions T provide the driving pulley 117 and the back-up pulleys 119 a and 119 b with resultant forces P and Q, respectively.
  • the sum of the vertical component forces of the back-up pulleys 119 a and 119 b and the driving pulley 117 is zero since the back-up pulleys 119 a and 119 b are disposed opposite to each other and a phase of the winding angle is an opposite phase with respect to the axis C described above.
  • the horizontal component force P applied to the driving pulley 117 and the horizontal component force Q H applied to each of the back-up pulleys 119 a and 119 b are biased horizontal component forces P+2Q H constitute a force causing the shaft tilting of the motor shaft.
  • the back-up forces Q′ and Q′, applied to the driving pulley 117 , of the back-up pulleys 119 a and 119 b are substantially stretched toward the center (rotation axis) of the motor shaft 115 a .
  • the problem of the shaft tilting can be solved when the biased horizontal component forces P+2Q H can be cancelled.
  • the back-up forces Q′ and Q′ of the back-up pulleys 119 a and 119 b are not necessarily applied toward the center of the motor shaft 115 a as the shaft axis of the driving pulley 117 .
  • these back-up pulleys are required to be disposed at substantially symmetrical positions with respect to the axis C, so that it is necessary to dispose the back-up pulleys within ⁇ 5 degrees of deviation from their positions with respect to the motor shaft.
  • the back-up pulleys 119 a and 119 b may only be required to satisfy arrangement and contact force relationships so as to provide such a force relationship that the sum of contact forces between the back-up pulleys and the shaft to be protected from the shaft tilting can cancel the sum of the vertical component forces and the sum of the horizontal component forces.
  • the back-up pulleys 119 a and 119 b are brought into contact the driving pulley 117 via the belt 116 so as to increase an amount of winding of the belt 116 around the driving pulley 117 .
  • the back-up forces Q′ and Q′ are applied to the driving pulley 117 so as to cancel the force applied toward the direction of the shaft tilting of the motor shaft 115 a caused by the belt tension.
  • This shaft tilting alleviating constitution can improve not only the stability of the rotation of the belt, but also the shaft tilting alleviating effect by increasing the amount of belt winding.
  • the force for cancelling the force toward the shaft tilting direction is applied from the back-up pulleys or the like, but in the present invention, a comparable force is not always have to be applied. Even a force which is not the comparable force can achieve the shaft tilting alleviating effect.
  • the back-up pulleys are disposed so as to increase the belt winding amount.
  • the back-up pulleys cannot increase the belt winding amount, it is possible to achieve the shaft tilting alleviating effect by disposing the back-up pulleys at positions so that their pressing portions are located closer to the idler pulley than the rotational center (rotation axis) of the driving pulley.
  • cross-sectional configurations of the driving pulley 117 and the back-up pulleys 119 a and 119 b at the belt winding portion are a positive crowning (convex) configuration and a negative crowning (concave) configuration, respectively, as shown in FIG. 9 , so that lateral deviation of the belt is regulated with respect to a thrust direction by pitching the flat belt 116 between the driving pulley and the back-up pulleys. It is also possible to employ the negative crowning configuration for the driving pulley and the positive crowning configuration for the back-up pulleys.
  • the rib When the thrust regulation of the belt is performed by an ordinary pulley rib, the rib can be broken during continuous use by rubbing with respect to the metal-made belt 116 set to have the high tension. In the present invention, it is possible to provide a lateral deviation preventing function without employing a complicated lateral deviation preventing mechanism.
  • FIG. 10 is a schematic front view of a speed reducing mechanism portion of the driving system 210 for the transfer belt 31 as the rotatable member. Also in this driving system 210 , the rotational speed of the motor shaft 201 a of the transfer belt driving motor (driving source) 201 is reduced by using a driving pulley (first pulley) 202 , transfer belt pulley (second pulley) 203 having a larger diameter than the driving pulley 202 , and a metal-mode flat belt 204 stretched between these pulleys 202 and 203 as a speed reducing mechanism.
  • driving pulley first pulley
  • second pulley transfer belt pulley
  • metal-mode flat belt 204 stretched between these pulleys 202 and 203 as a speed reducing mechanism.
  • tensioner rollers 205 a and 205 b and back-up pulleys (pressing members) 206 a and 206 b are disposed, so that tension is applied to the belt 204 and the shaft tilting of a motor shaft 201 a is alleviated.
  • a reference symbol G represents a line connecting a shaft axis H of the driving pulley 202 as a drive-side pulley and a shaft axis I of the transfer belt pulley 203 as a follower-side pulley.
  • the tensioner rollers 205 a and 205 b for applying tension to the belt 264 stretched between the driving pulley 202 and the transfer belt pulley 203 are disposed at substantially symmetrical positions with respect to the axis G. These tensioner rollers 205 a and 205 b are pressed against the outer surface of the belt 204 by tension springs 207 a and 207 b , respectively, to the tension to the belt 204 .
  • the problem of the shaft tilting is solved by providing the back-up pulleys 206 a and 206 b for alleviating the shaft tilting of the motor shaft 201 a.
  • the back-up pulleys 206 a and 206 b are disposed at substantially symmetrical positions with respect to the above-described axis G and are pressed against the driving pulley 202 through the belt 204 interposed therebetween.
  • the back-up pulleys 206 a and 206 b are disposed so as to not only increase the winding amount of the belt 204 around the driving pulley 202 , but also be pressed substantially from the transfer belt pulley 203 side toward the shaft axis of the driving pulley 202 .
  • the back-up pulleys 206 a and 206 b are rotatably supported by rotatably swingable arms 209 a and 209 b , respectively, with shaft portions 208 a and 208 b as centers of the rotation. Further, the swingable arms 209 a and 209 b are rotationally urged toward the driving pulley 202 by pressing springs 210 a and 210 b , respectively, to press the back-up pulleys 206 a and 206 b against the driving pulley 202 through the belt 204 .
  • the back-up pulleys 206 a and 206 b apply back-up forces from outside of the belt 204 to the driving pulley 202 so that the resultant of forces is zero in a force relationship with the belt tension.
  • the back-up forces and the like they are similar to those in the case of the speed reducing mechanism ( FIGS. 4 to 9 ) for the above-described drum driving system 110 , so that the description thereof will be omitted.
  • the constitution of this embodiment it is possible to not only prevent the shaft tilting but also increase an angle (amount) of winding of the belt around the pulley, so that a shaft tilting force between the belt and the pulley can be increased.
  • the belt is made of metal, so that belt shrinkage is less and thus it is possible to perform stable shaft tilting.
  • the image forming apparatus representing the precision equipment by using the belt drive transmission apparatus as a process driving apparatus for the photosensitive drum and the transfer belt, a high-quality output image free from color misregistration and image non-uniformity can be obtained.
  • the back-up pulleys 119 a and 119 b are constituted to function also as the tensioner rollers.
  • the back-up pulleys 119 a and 119 b are rotatably with respect to the swingable arms 123 a and 123 b rotatable around the motor shaft 115 a and are slidably movable along an elongated hole (slit) formed in each of the arms with respect to a longitudinal direction of the arm.
  • the swingable arms 123 a and 123 b are rotationally urged against the driving pulley 117 by back-up springs 124 a and 124 b , respectively, so that the back-up pulleys 119 a and 119 b are pressed against the driving pulley 117 via the belt 116 .
  • the back-up pulleys 119 a and 119 b are pressed against the outer surface of the belt 116 to apply tension to the belt 116 .
  • the speed reducing mechanism constitution of the drum driving system 110 in this embodiment is also applicable to the transfer belt driving system 210 in Embodiment 1.
  • Embodiments 1 and 2 it was possible to prevent the shaft tilting and increase the belt winding amount by providing the back-up pulleys 119 a and 119 b ( 206 a and 206 b ) with respect to the drive-side pulley 117 ( 202 ). It is also possible to expect a similar effect even in a constitution such that the back-up pulleys 119 a and 119 b ( 206 a and 206 b ) are provided with respect to the follower-side pulley 112 ( 203 ) to prevent the shaft tilting and increase the belt winding amount.
  • the back-up pulleys 119 a and 119 b are pressed from the drive-side pulley toward the follower-side pulley shaft axis (axial line). Further, it is also possible to expect the similar effect even in a constitution such that the back-up pulleys 119 a and 119 b ( 206 a and 206 b ) are provided with respect to both of the drive-side pulley 117 ( 202 ) and the follower-side pulley 112 ( 203 ) to prevent the shaft tilting and increase the belt winding amount. Further, in the above described Embodiments, the back-up members are provided with respect to the drive-side pulley, but the shaft tilting alleviating effect can also be achieved by providing the back-up members with respect to the follower-side pulley.
  • Embodiments 1 and 2 it was possible to obtain a large effect by using the metal-made flat belts as the drive transmission belts 116 , 113 a - 113 d , and 204 and by employing the above-described back-up constitution. However, it is also possible to achieve a substantially similar effect even when a toothed belt, a V-belt, an elastic rubber belt, or the like is used as the drive transmission belt.
  • the rotatable member is the rotation shaft for rotating another pulley, but the rotatable member can be the rotation shaft of the photosensitive member as the rotatable member. Similarly, the rotatable member can be a shaft of the driving roller for driving the intermediary transfer member.
  • Embodiments 1 and 2 the usefulness of the present invention is described with respect to the belt drive transmission apparatus in the color image forming apparatus which is a representative apparatus as the precision equipment.
  • the belt drive transmission apparatus in the present invention can also achieve a similar effect even when the belt drive transmission apparatus is used in apparatuses, other than the color image forming apparatus, such as other precision machines, electrical appliances, and mechanical apparatuses.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrophotography Configuration And Component (AREA)
  • Devices For Conveying Motion By Means Of Endless Flexible Members (AREA)
  • Discharging, Photosensitive Material Shape In Electrophotography (AREA)
US11/953,376 2006-12-14 2007-12-10 Image forming apparatus whose image bearing member is rotated by a pulley Expired - Fee Related US7856195B2 (en)

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JP2006336967A JP4871716B2 (ja) 2006-12-14 2006-12-14 駆動伝達装置
JP2006-336967 2006-12-14

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100054781A1 (en) * 2008-09-01 2010-03-04 Ricoh Company, Limited Transfer device and image forming apparatus
US20110033206A1 (en) * 2009-08-07 2011-02-10 Canon Kabushiki Kaisha Driving force transmitting device and image forming apparatus including the same
US20200218177A1 (en) * 2019-01-08 2020-07-09 Kyocera Document Solutions Inc. Belt drive device capable of restricting damage of belt, image forming apparatus
US20240401687A1 (en) * 2023-01-31 2024-12-05 Belt Technologies, Inc. Belt Pulley Assembly

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5900796B2 (ja) * 2012-03-21 2016-04-06 株式会社リコー 駆動装置及び画像形成装置
US9423002B2 (en) 2013-05-28 2016-08-23 Kyocera Document Solutions Inc. Metal belt and driving mechanism with same metal belt
JP7174344B2 (ja) * 2018-07-26 2022-11-17 株式会社リコー 画像形成装置
JP7471850B2 (ja) * 2020-02-19 2024-04-22 キヤノン株式会社 記録装置および搬送方法

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US518314A (en) * 1894-04-17 Ferdinand a
JPS6280648A (ja) 1985-10-04 1987-04-14 Fuji Photo Film Co Ltd 画像形成方法
US5216475A (en) * 1991-03-04 1993-06-01 Canon Kabushiki Kaisha Pulley driven image forming apparatus
JPH06161205A (ja) 1992-11-19 1994-06-07 Canon Inc 画像形成装置
JP2004183860A (ja) 2002-12-06 2004-07-02 Ricoh Co Ltd 駆動力伝達装置、駆動装置及び画像形成装置

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US518314A (en) * 1894-04-17 Ferdinand a
JPS6280648A (ja) 1985-10-04 1987-04-14 Fuji Photo Film Co Ltd 画像形成方法
US5216475A (en) * 1991-03-04 1993-06-01 Canon Kabushiki Kaisha Pulley driven image forming apparatus
JPH06161205A (ja) 1992-11-19 1994-06-07 Canon Inc 画像形成装置
JP2004183860A (ja) 2002-12-06 2004-07-02 Ricoh Co Ltd 駆動力伝達装置、駆動装置及び画像形成装置

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100054781A1 (en) * 2008-09-01 2010-03-04 Ricoh Company, Limited Transfer device and image forming apparatus
US8385762B2 (en) * 2008-09-01 2013-02-26 Ricoh Company, Limited Transfer device and image forming apparatus
US20110033206A1 (en) * 2009-08-07 2011-02-10 Canon Kabushiki Kaisha Driving force transmitting device and image forming apparatus including the same
US8437662B2 (en) * 2009-08-07 2013-05-07 Canon Kabushiki Kaisha Driving force transmitting device and image forming apparatus including the same
US20200218177A1 (en) * 2019-01-08 2020-07-09 Kyocera Document Solutions Inc. Belt drive device capable of restricting damage of belt, image forming apparatus
US10895830B2 (en) * 2019-01-08 2021-01-19 Kyocera Document Solutions Inc. Belt drive device capable of restricting damage of belt, image forming apparatus
US20240401687A1 (en) * 2023-01-31 2024-12-05 Belt Technologies, Inc. Belt Pulley Assembly

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JP2008151165A (ja) 2008-07-03
US20080145101A1 (en) 2008-06-19

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